The present invention is directed to a UV dryer used to cure coatings disposed on multiple surfaces of three-dimensional products.
Ultraviolet curing uses intense ultraviolet(UV) light instead of heat to cure inks, coatings or adhesives in a very wide range of applications. Called photopolymerization, the UV curing process is photochemical, using liquid monomers and oligomers mixed with a small percent of materials called photoinitiators. When exposed to UV radiation, they instantly harden, becoming the decorative inks, tough clear coats, adhesives with a variety of properties, and many other materials filling a wide range of industrial needs.
UV radiation may be generated by microwave powered electrodeless lamps generally comprising a microwave chamber in which a longitudinally extending bulb envelope containing a plasma forming medium is disposed. The microwave chamber is comprised of a reflector for reflecting light emitted by the envelope and a mesh which is opaque to the microwave energy within the chamber, but transparent to the emitted light for allowing it to exit therefrom. The lamp is excited by microwave energy which is generated by one or more magnetrons which are coupled to the chamber through coupling slots located in the reflector.
The above described UV lamps are effective in curing coatings on generally planar two-dimensional surfaces. These surfaces are typically arranged to pass underneath the dryer in substantially perpendicular orientation to the radiation from the lamp, thereby providing essentially equal amounts of energy for an effective cure. However, when the coatings to be cured are not disposed on a single plane but are, instead, disposed on multiple surfaces at different orientations, each surface would receive different amounts of energy, depending on the orientation and distance of the surfaces relative to the lamp.
There is, therefore, a need for a UV lamp that can cure coatings disposed on multiple surfaces of a product.
It is an object of the present invention to provide a dryer for curing multiple surfaces of three-dimensional products without the necessity of reconfiguring lamps between passes, use of robots, etc.
It is another object of the present invention to provide a dryer for curing the leading and trailing surfaces of three-dimensional products by providing a pivoting motion to the dryer as the product moves along a conveyor underneath the dryer.
In summary, the present invention provides a UV dryer for curing multiple surfaces of a three-dimensional product comprising a plurality of UV lamps connected end-to-end to form an assembly having a longitudinal axis. Each lamp includes a tubular envelope aligned along the longitudinal axis. The assembly is pivotable along the longitudinal axis at a xc2x1 angle, preferably 45xc2x0, from a vertical plane containing the longitudinal axis to direct radiation from the assembly toward a leading, top and trailing surface of the product as the product is moved toward, underneath, and away from the assembly, respectively.
These and other objects of the present invention will become apparent from the following detailed description.